Lighting system



p 969 c. D. SKIRVIN 3,467,887

LIGHTING SYSTEM Filed Aug. 28, 1 967 3 Sheets-Sheet l 25 44 21 22 T L if 22 w 6 .L (-1 60 1 r:

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LIGHTING SYSTEM Filed Aug. 28, 1967 3 Sheets-Sheet 2 F- .3 Y 30 32 24 2a 34- 36 U Sept. 16, 1969 Filed Aug. 28. 1967 C. D. SKIRVIN LIGHTING SYSTEM 5 Sheets-Sheet 5 M/l rfA/TUR" em /54a 56/210)! Arron/var;

United States Patent ABSTRACT OF THE DISCLOSURE This invention relates to a lighting. system in which a direct voltage of a relatively low value is usedto illuminate a luminescent tube such as a fluorescent tube. The system includes a current control member such as a transistor which is normally biased to a state of conductivity.

A first reactance such as the primary winding of a transformer is connected to the source of direct voltage and to the transistor to store energy duringthe timethat the transistor is conductive. A second reactance such as a capacitor is also connected to the current control member and the primary winding of the transformer to store energy during the time that the transistor is conductive.

When the capacitor becomes charged to a particular value, it starts to discharge through a second current control member such as a diode which is connected to the transistor and which is connected in a circuit with the primary winding of the'transformer and the capacitor. During the time that the capacitor is discharging through the diode, the transistor is biased to a state of nonconductivity.

In this way, the transistor is alternately triggered to the conductive and nonconductive states. When the transistor is triggered to the nonconductive state, the low impedance provided by the diode across the primary winding of the transformer prevents the electromotive force in the transformer from producing voltage surges which would tend to damage the transformer.

The transformer has a secondary winding which is connected across the luminescent tube to illuminate the tube. During the time that the transistor is conductive, a current flows through the secondary winding and the luminescent gas to excite the gas in the tube. When the transistor becomes nonconductive, the energy stored in the transformer discharges through the luminescent tube.

The transformer may have a third winding when the luminescent tube has a filament. This third winding is connected across the filament and in a circuit with the transistor. This causes the third winding to provide a relatively low impedance across the filament during the time that the transistor is conductive. Thislow impedance tends to limit the flow of current through the filament. However, when the transistonis nonconductive, the third winding provides a high impedance across the filament so that a relatively great current flows through the filament. In this way, the filamentreceives an alternating current so as to become heated and emit electrons for exciting the tube.

This invention relates to a lighting system employing a direct voltage of relatively low amplitude toilluminate a luminescent tube such as a fluorescent tube. The invention is especially advantageous since it provides a relatively low drain of power on the'source of direct voltage so that the luminescent tube can continue to be illuminated for a relatively great period of time such as several hours without requiring that the source of direct voltage be recharged.

The safety codes of all buildings in major cities provide that exit lights be illuminated at all times to indicate to 3,467,887 Patented Sept. 16, 1969 "ice those in the buildings where exits are located in the buildings in case of emergency. The exit lights are energized normally by the power introduced to the building from the main power lines which carry alternating current. The systems energizing such exit lights include a battery which is charged by the signals in the main power lines during the time that power is available in these lines. However, if there should be a power failure of any kind, the batteries provide energy to the exit lights to obtain an illumination of the exit lights.

Systems are also desired which can be carried by people in an oflice or in a home in case of a power failure. For example, even in this day of advanced technology, people have tO'light candles in their homes in case of a p w failure. The use of candles is inefficient since the candles do not provide very much illumination. Furthermore, candles are dangerous since they involve the use of a flame open to the atmosphere.

Various attempts have been made to provide exit lights or portable lights but these attempts have not been completely successful for various reasons. One reason is that the exit lights now in use have not been able to provide an illumination for any extended length of time after a power failure has occurred. Another reason is that the systems for operating the exit lights now in use are fairly complicated. The same problems exist with respect to the portable lights now in use.

This invention provides a system for energizing an exit light or a portable light for an extended period of time such as several hours after a power failure has occurred. This results from the operation of the system constituting this invention to drain energy from a source of direct voltage such as a battery at a relatively low rate. The system is also advantageous, since it uses a minimum number of parts and since it provides certain compensating features to regulate the energizing of the luminescent tube even when the characteristics of the luminescent tube vary from one unit to the next, and even when the characteristics of each individual luminescent tube vary with age.

The system including this invention has a first current control member such as a transistor which is normally biased to maintain the transistor in the conductive state. First reactance means such as a transformer are connected to the transistor and to the source of direct voltage to introduce a voltage to the transistor for triggering the transistor to a state of conductivity from a nonconductive state. When the transistor becomes conductive, current flows through a circuit including the transistor, the transformer and the source of direct voltage. Current also flows through a circuit including the transistor, the transformer and second reactance means such as a capacitor. The flow of current through the capacitor and the transformer causes energy to be stored in the transformer and in the capacitor.

When the energy stored in the capacitor reaches a particular level, the capacitor becomes discharged through a second current control member such as a diode. The diode is connected to the transistor so as to bias the transistor to a state of nonconductivity by the forward impedance across the diode when the diode is conductive. In this way, the diode maintains the transistor nonconductive during the time that the capacitor is discharging through the transistor. Upon becoming discharged to a relatively low level, the bias normally produced in the transistor is able to become operative to trigger the transistor to a state of conductivity.

In this way, the transistor becomes alternately conductive and nonconductive at a particular frequency dependent upon the characteristics of certain elements including the value of the capacitor. The waveform produced in the transformer by the alternate production of conductive and nonconductive states in the transistor is nonsinusoidal so that the signal in the transformer has a fundamental frequency and also has harmonics. The fundamental frequency and the harmonics are instrumental in exciting the gas in the luminescent tube to produce an illumination in the tube. a

Various embodiments are provided for the system constituting this invention. In one embodiment, the luminescent tube is provided with a filament constructed to emit electrons when heated. An additional winding is provided in the transformer and is connected across the filament to produce an alternating current through the filament for exciting the filament to emit electrons. The alternating current is produced in the filament because of the operation of the transistor in becoming alternately conductive and nonconductive. In a second embodiment, the additional winding may be used as a choke when the luminescent tube does not have a hot cathode which is energized upon becoming heated.

In another embodiment of the invention, an additional portion is included in the primary winding of the transformer. This portion is connected in the circuit in a relationship to minimize any flow of direct current through the circuit. As will be appreciated, a direct current is not advantageous in the circuit since it does not aid in the formation of the alternating signal in the transistor. Furthermore, the direct current tends to drain the source of direct voltage so as to minimize the time in which the luminescent tube can be illuminated by power from the source of direct voltage.

In the drawings:

FIGURE 1 is a circuit diagram of one embodiment o the invention;

FIGURE 2 illustrates the voltage waveform introduced to the luminescent tube in FIGURE 1;

FIGURE 3 is a circuit diagram of a second embodiment of the invention;

FIGURE 4 is a circuit diagram of a third embodiment of the invention;

FIGURE 5 illustrates the voltage waveforms produced at strategic terminals in the embodiment shown in FIG- URE 4; and

FIGURE 6 is a circuit diagram of a fourth embodiment of the invention.

In the embodiment of the invention illustrated in FIG- URE 1, alternating voltage is introduced from power lines 10 through a transformer 12 to a rectifier 14. The transformer 12 may be adapted to reduce the voltage on the lines 10 from a value such as 115 volts RMS to a suitable value such as 5 volts RMS. The rectifier 14 may constitute a whole wave or a half wave rectifier of known construction. The output from the rectifier 14 is introduced to a source of direct voltage such as a battery 16 which may be formed from a plurality of nickel cadmium battery cells of known construction. The cells may be connected to provide a negative voltage on a line 18 and a positive voltage on a line 20.

The line 18 is connected to a terminal 21 at one end of a primary winding 22 of a transformer generally indicated at 24. The primary winding 22 has an intermediate tap 26 which is connected to an input electrode of a current control member. The input electrode may constitute an emitter when the current control member constitutes a transistor 28. A connection is also made from the intermediate tap 26 to a second current control member such as a diode 30. For example, the connection may 'be between the intermediate tap 26 and the plate of the diode 30. The control electrode of the first current control member such as the base of the transistor 28 is connected to the cathode of the diode 30 and is also connected to one plate of a capacitor 32, the second plate of which is connected to a terminal 33 at the other end of the primary winding 22. The base of the transistor 28 is also connected to one terminal of the resistor 34, the other terminal of which-is connected to the collector of the transistor.

The transformer 24 also has a secondary winding 36 which is connected with a capacitor 38 in a circuit including the two electrodes of a luminescent tube 40. The luminescent tube may be a fluorescent tube of conventional construction. The transformer 24 further includes a tertiary winding 42 which is connected across a filament 44 in the tube 40. The filament 44 may be considered as one of the electrodes in the tube. The winding 42 and the filament 44 are connected between the positive line 20 of the battery 16 and the collector of the transistor 28. Since a negative voltage is introduced from the line 18 to the terminal 21 of the primary winding 22 in FIGURE 1 and since the terminal 33 of the primary winding is connected through the capacitor 32 and the resistor 34 and the winding 42 to the positive line 20, the terminal 33 of the primary winding in FIGURE 1 is more positive than the terminal 21 of the winding or than the intermediate tap 26. This causes the voltage on the base of the transistor 28 to become more positive than the voltage on the emitter of the transistor so that the transisor becomes conductive. The conductivity of the transistor 28 is facilitated by the operation of the resistor 34 in providing a bias between the base and collector of the transistor in a direction for facilitating the flow of current between the base and collector of the transistor. When the transistor 28 becomes conductive, current flows through a circuit including the battery 16 or the rectifier 14, the line 20, the tertiary winding 42, the collector and emitter of the transistor 28 and the portion of the primary winding 22 between the intermediate tap 26 and the terminal 21 in FIGURE 1. This flow of current is in a direction for inducing a voltage in the primary winding 22 in a direction for obtaining a positive voltage on the terminal 33 of the primary winding relative to the voltage on the intermediate tap 26. This voltage further biases the transistor 28 in a direction for producing a large flow of current through the transistor. Because of the voltage across the primary winding 22, current also flows through a circuit including the portion of the primary winding between the terminal 33 and the intermediate tap 26, the capacitor 32, the resistor 34 and the collector and emitter of the transistor 28. The capacitor 32 becomes charged by this flow of current such that a positive voltage is produced on its right plate and a negative voltage on its left plate.

When the capacitor 32 becomes charged to a particular value, the negative voltage on the left plate of the capacitor tends to bias the base of the transistor 28 to a voltage for producing a state of nonconductivity in the transistor. The capacitor 32 then starts to discharge through a circuit including the portion of the primary winding 22 between the terminal 33 and the tap 26 in FIGURE 1 and also including the diode 30. Because of the flow of current through the diode 30, a voltage drop is produced between the plate and cathode of the diode. Although this voltage drop is relatively low, it is sufiicient to bias the base and emitter of the transistor 28 in a direction for maintaining the transistor nonconductive. Since the diode 30 has a relatively low impedance when conductive, it provides a low impedance across the primary winding 22 to prevent voltage surges from being produced in the primary winding 22 when the transistor 28 becomes nonconductive. In this way, the transistor 28 cannot become damaged when it changes between the conductive and nonconductive states.

The waveform of the voltage produced in the primary winding 22 is illustrated in FIGURE 2. As will be seen at 50 in FIGURE 2, the waveform initially rises steeply as the voltage is applied from the battery 16 to the primary winding. When the transistor 28 becomes conductive, the resultant charging of the capacitor 32 and 22 cause the voltage in the primary winding 22 to decrease gradually, as illustrated at 52 in FIGURE 2.

A negative surge 54 is subsequently produced when the capacitor 32 has become charged to a suflicient value to make the diode 30 conductive and the transistor 28 nonconductive. The surge 54 has both a falling portion 54a followed by a rising portion 54b. The surge results from the electromotive force produced in the transformer 24 when the transistor 28 changes from a conductive to a nonconductive state.

At the end of the surge 54, a time interval occurs during which the energy stored in the transformer 24 during the conductivity of the transistor 28 is discharged through the luminescent tube 40. This time period is illustrated at 56 in FIGURE 2. Thereafter, a new cycle of operation is initiated by a voltage surge 50 similar to the voltage surge 50 described above.

Since the tertiary winding 42 is magnetically coupled to the primary winding 22, its impedance is controlled by the flow of current through the primary winding. For example, the impedance of the tertiary winding 42 is relatively low during the time that current is flowing through the transistor 28 and the primary winding. Since the low impedance provided by the winding 42 is across the filament 44, relatively little current flows through the filament. However, when the transistor 28 becomes nonconductive so that relatively little current flows through the primary winding 22, the impedance provided by the tertiary winding 42 is relatively high. This causes a relatively great current to. flow through the filament 44 since the impedance of the filament is relatively low and since the filament is, in effect, shunted by an open circuit represented by the winding 42. In this way, the filament 44 receives an alternating current even though it is connected to a source of direct voltage.

As will be seen, the direct voltage from the ,rectifier 14 or the battery 16 is converted to an alternating voltage. This alternating voltage has a fundamental frequency of a relatively high value such as in the order of 23 kilocycles. The gas in the tube 40 becomes excited when subjected, to a voltage at this relatively high frequency so as to produce an ionization of the gas in the tube and a resonance of the ionized particles. The resonance is facilitated by the harmonies which occur in the signal illustrated in FIGURE 2. The harmonics are also instrumental in initially exciting the gas in the tube. Because of the excitation of the gas in the tube to produce an ionization of the gas and the resonance of the ionized particles, the tube 40 produces a relatively great illumination with the expenditure of relatively little energy. I

As will be seen from the above discussion, substantially no direct current flows through the system illustrated in FIGURE 1 whether the system is'ene rgized by the rectifier 14 or the battery 16. Furthermore, the alternating current flowing through the system hasa relatively low amplitude. This results in part because of the relatively high frequencies produced in the system to energizethe tube 40 and because of the harmonics produced in the system to resonate the gas in the tube 40. Since substantially no direct direct current and an alternating current of relatively low amplitude flow through the system, the system is able to operate for ext ended periods of time such as several hours to energize the tube 40 even when a power failure interrupts the supply of energy from the source so that energy has to be supplied to the circuit entirely by the battery 16. l i I In addition to the advantages discussed above, the system illustrated in FIGURE l-and disclosed above provides its own regulation. For example, the frequency of the alternating signal illustrated in FIGURE 2 may tend to vary as the tube 40 and the other elements in FIGURE 1 age. For example, the frequency of the sig nal illustrated in FIGURE 2 may increase. This would tend to produce an increased impedance in the winding 42 when the transistor 28 is triggered from the conductive state to the nonconductive state. This increased impedance in the winding 42 would tend to increase the current through the filament 44. The current through the filament 44 might increase to such an extent that the tube 40 would become damaged or at least its life would be shortened. However, since the transformer 24 releases its stored energy by a flow of current through the secondary winding 36 and the tube 40 when the transistor 28 becomes nonconductive, any increase in such current flow tends to limit any increase in impedance across the winding 42. This limits any tendency of the filament 44in the lighting tube to become overheated since the impedance across the winding 42 controls the amplitude of the current through the filament.

It may sometimes occur that the filament 44 of the tube 40 may become impaired by an extended operation of the. tube. The tube 40 would still tend to become illuminated at a time near the peak in each alternating cycle because of the discharge of energy in the transformer 24 through the winding 36 and the tube 40. When the tube 40 becomesilluminated, it tends to draw a normal current through the remainder of each alternating cycle. The result would be that the tube would require a longer time in each cycle to become illuminated than with a normal filament but the tube would continue to operate in its normal manner for the remainder of the cycle.

At times, the continuous circuit between the winding 36 .and the tube 40 may become interrupted because of defects in parts or in workmanship. Since the winding 36-,does not now limit the flow of current through the filament 44, the flow of current through the filament may tend to become excessive and eventually impair the filament. At such a time, both the windings 36 and 42 would experience open circuits. The resultant impedances across the windings 36 and 42 would be relatively great during the time that the transistor 28 is nonconductive. These high impedances would tend to limit the currents drawn from the rectifier 14 or the battery 16 so that the life of the battery would not be materially impaired.

Sometimes the circuit across the winding 36 or across the winding 42 or across both windings may become short circuited. For example, a short circuit may sometimes occur across the winding 42. This would tend to increase the current in a manner similar to that described above for an increase in current through the filament 44. However, the winding 36 would still tend to produce a current through the tube 40 during the time that the transistor 28 is nonconductive. This current would tend to limit the impedance across the winding 42 so as to limit the current drawn from therectifier 14 or the battery 16 as described above.

At relatively low temperatures, the resistance of the filament 44 is reduced compared to that at normal temperatures. This tends to increase the current through the filament 44 so that the ease of initially exciting the tube 40 becomes enhanced. If the temperature of the filament 44-increases, the resistance of the filament accordingly increases and limits the current flowing through the filament. This tends to increase the difliculty of igniting the tube 40. In this way, the temperature of the filament is compensated in the operation of the tube so that a regulating action is provided on this operation.

In onev embodiment of the invention, the following values and elements were used to accomplish the results dsecribed above in detail:

Winding 22 (between terminal 21 and tap 26)-16 turns of No. 24 wire.

Winding 22 (between tap 26 and terminal 33)-22 turns 1 of No. 24 wire.

Winding 36350 turns of No. 36 wire Winding 42l6 turns of No.24 wire Diode 30-a silicon diode such as a Type SD05 manufactured by Diodes, Inc.

7 Transistor 28Type MJESZO manufactured by Motorola Capacitor 320.1 microfarad Resistor 3410 kilohm Capacitor 38-0.01 microfarad A capacitor 60 is illustrated in broken lines in FIG- URE 2 as being connected between the terminal 21 of the primary winding 22 and the winding 42. This capacitor is shown in broken lines since it is connected on an optional basis in the system shown in FIGURE 1. The capacitor 60 may be provided with a suitable value such as approximately 0.22 microfarad. One purpose of including the capacitor 60 is to insure that noise is suppressed in the system shown in FIGURE 1 so that the operation of adjacent radio and television receivers will not be impaired.

It will be appreciated that tubes may be provided which do not have a hot cathode or filament such as the filament 44. Under such circumstances, the system shown in FIG- URE 1 may still be used. This system is illustrated in FIGURE 3 for purposes of convenience. The tertiary winding 42 now serves as a choke during the flow of current through the transformer 24 and the transistor 28 to limit this flow of current. The winding 42 further serves as a noise suppressor to limit any surges of voltage across the transistor, thereby preventing buzzes or static in nearby electronic equipment such as radios. Although the tertiary Winding 42 is shown in FIGURE 3 as being magnetically coupled to the windings 22 and 36, it will be appreciated that the winding 42 can serve as a choke without being magnetically coupled to the other windings in the transformer 24.

The system shown in FIGURE 4 constitutes a further modification of the systems shown in FIGURES 1 and 3. The system shown in FIGURE 4 includes a primary winding 22 and a secondary winding 36, a transistor 28, a diode 30 and a capacitor 32 in a manner similiar to that described above. However, the winding 42 is in effect attached to the bottom of the primary winding 22 in FIGURE 1 to form an additional portion 22a at the bottom end of the winding. This portion is defined by an intermediate tap 100 and an end terminal 101 at the bottom of the winding in FIGURE 1. The connections to the additional portion 22a of the primary winding 22 correspond to those shown in FIGURE 1 and described above except that a filament corresponding to the filament 44 is not connected across the portion 22a.

The system shown in FIGURE 4 operates in a manner similar to that shown in FIGURE 1. The voltage introduced to the winding 22 from the rectifier 14 or the battery 16 causes the transistor 28 to become conductive. The resultant flow of current through the capacitor 32 and the primary winding 22 causes the capacitor and the transformer 24 to store energy. When the energy stored in the capacitor 32 reaches a particular value, the capacitor discharges through the diode 30 to make the transistor 28 nonconductive. The transistor 28 continues to be nonconductive until the capacitor 32 has discharged somewhat. The bias then produced in the transistor then becomes predominant and the transistor becomes conductive to initiate a new cycle of operation.

The system shown in FIGURE 4 differs from the system shown in FIGURE 1 in the paths in which the currents flow at different times in each cycle of operation. For example, during the time that the transistor 28 is conductive, current flows through a circuit including the portion of the primary winding 22 between the tap 26 and the terminal 33 in FIGURE 4, the capacitor 32, the resistor 34 and the collector and emitter of the transistor 28. This current is in an upward direction in FIGURE 4 through the primary winding 22. Current also flows downwardly through the primary winding between the intermediate taps 26 and 100. This flow of current occurs through a circuit including the portion of the primary winding between the intermediate tap 26 and the terminal 101 of the primary winding in FIGURE 4, a capacitor 103 and the collector and emitter of the transistor 28. The number of turns in the primary winding between the intermediate tap 26 and the terminal 101 of the winding in FIGURE 4 is greater than the number of turns between the intermediate tap 26 and the terminal 33 of the winding in FIGURE 4. Furthermore, the value of the capacitor 103 is less than the value of the capacitor 32. Because of this, the current flowing downwardly through the primary winding 22 in FIGURE 4 is greater than the current flowing upwardly through the primary winding during the time that the transistor 28 is conductive. This current flow is illustrated at 110 in FIGURE 5.

The capacitor 103 becomes charged by the flow of current through it in a manner similar to that described above for the capacitor 32. The charge is in a direction such that the right plate of the capacitor 103 is more positive than the left plate of the capacitor. Accordingly, when the transistor 28 becomes nonconductive, current flows through a circuit including the lower portion of the winding 22 in FIGURE 4, a filter capacitor 106 and the capacitor 103 to discharge the capacitor 103. The flow of current is upwardly through the winding 22. This is in a direction opposite to the current flowing through the lower portion of the winding 22 in FIGURE 4 when the transistor 28 is conductive. The current flowing through the capacitor 32 and the upper portion of the winding 22 to discharge the capacitor 32 is also in an upward direction in FIGURE 4.

Because of the upward flows of current through the primary winding 22 in FIGURE 4 during the time that the transistor 28 is nonconductive, a current illustrated at 112 in FIGURE 5 is produced. Since the current 112 has an opposite polarity to the current 110 which flows through the winding 22 during the time that the transistor 28 is conductive, the current 112 helps to minimize any direct current components in the transformer. This insures that the drain on the battery 16 will be minimal when the battery is supplying energy to light the lamp 40. In effect, the Q of the transformer 24 is increased by providing the portion of the winding between the tap and the terminal 101 of the winding in FIGURE 4.

By varying the values of the capacitors 32 and 103, the duty cycle or frequency of the signal introduced to the tube 40 can be adjusted through a relatively great range such as between approximately 30 kilocycles and 250 kilocycles. If the values of the capacitors 32 and 103 are increased, the frequency of the signal is decreased since the capacitors receive an increased charge and the time required for the capacitors to discharge increases. If only the value of the capacitor 100' is increased, the frequency is decreased but the width of the signal is increased. This results from the fact that the current flow ing through the transistor 28 is decreased so that decreased currents flow through the capacitors 32 and 103 and require increased times to charge these capacitors to particular values. An increase in the value of the capacitor 103 also increases the amplitude of the signal 112 since the capacitor 103 in effect serves as a battery and receives an increased voltage because of its increased capacity. However, the width of the signal 112 is not affected appreciably by changing the value of the capacitor 103.

Preferably the number of turns between the tap 26 and the terminal 33 of the primary winding 22 in FIG- URE 4 is approximately equal to the number of turns between the intermediate tap 103 and the terminal 101 of the winding. One purpose of providing such a ratio is to insure that the transistor 28 will be switched properly between the conductive and nonconductive states. If the transistor 28 does not receive a sufficient voltage between its base and emitter relative to the voltage between the base and collector, the transistor will be starved from conducting. If the transistor receives too high a voltage between the base and emitter relative to the voltage between the base and collector, the transistor will become saturated easily and will not be triggered sufficiently fast to the nonconductive state. Under such circumstances, the transistor will tend to overheat.

FIGURE 6 represents a combination of the circuits shown in FIGURES 1 and 3 or a combination of the circuits shown in FIGURES 1 and 4. The embodiment shown in'FIGURE 6 is similar to that shown in FIGURE 4 but includes the winding 42 shown in FIGURES 1 and 3. When the luminescent tube 40 has a hot cathode, the winding 44 is connected as illustrated in FIGURE 4. The operation of the embodiment shown in FIGURE 6 will be understood from the description given above for the previous embodiments.

Although this application has been disclosed and illustrated with reference to particular applications,the principles involved are susceptible of numerous other applications which will be apparent to persons skilled in the art. For example, the invention may be used as an inverter into resistance loads and/or inductance loads such as incandescent lamps, vibrators and controlled frequency power devices. The invention is, therefore, to be limited only as indicated by the scope of the appended claims.

What is claimed is:

1. In combination for illuminating a luminescent tube,

" a source of direct voltage,

a first cu'rrent control member having conductive and nonconductive states and having control, input and output electrodes, R

first reactance means coupled electrically to the source of direct'voltage and to the input electrode of the first curre nt control member for biasing the input electrode with a voltage of a particular polarity,

second reactance means constructed to store energy,

first means including the second reactance means connected in a electrical circuit with the source of voltage and the first reactance means for biasing the control electrode of thefirst current control member witha particular voltage relative to the voltage on the input electrode of the first current control memher to product a stateofconductivity in the first current control member and a storage of energy in the first and second reactance means,

' a second current control member having conductive and] nonconductive states,

secondmcans connecting the second current control member in an electricalcircuit with the first and second reactancemeans between the control and inr put electrodes ofv the first current control member for, biasing the first current control member to a state of nonconductivity. upon the storage of a particular amountof energy in-the.second reactance means and for providing adischarge of the energy in the second reactance means through the second current control member and the first reactance me'ans upon a state of nonconductivity in the first current control member to obtain a subsequent 1 state" -of conductivity -ir i the first current 7 control member, and I i third means connecting the luminescent tube to the first reajctanc e means to" obtain a flow of current through the luminescent tube during the state of conductivity in the first current control member and to f obtain. a discharge through the luminescent tube, duringthestate of conconductivity in the first currcnt. control member, of the energy stored in the first reactance means.

,2 The combination set forth in claim 1 wherein the first reactance means is inductive and the second reactance means is capacitive.

a 3. In combination for'illuminating a luminescent tube,

a source of direct voltage,

a first current control member having conductive and nonconductive states,

a second current control member having conductive and nonconductive states,

first reactance means constructed to store energy,

second reactance means constructed to store energy,

means connected in electrical circuitry with the first and second reactance means and the source of direct voltage to bias the first current control member to the state of conductivity and to obtain a storage of energy in the first reactance means and a storage of energy in the second reactance'means during the state of conductivity in the first current control member,

means conducted in electrical circuitry with the first and second reactance means and the second current control member for producing a discharge through the second current control member of the energy stored in the second reactance means upon the storage of a particular amount of energy in the second reactance means to bias the first current control member to the state of noncondu-ctivity du-ring the discharge of the energy in the second reactance means through the second current control member and to obtain the state of conductivity in the first current control member after such discharge, and

means connecting the luminescent tube to the first reactance means to obtain a flow of current through the first reactance means and the luminescent tube during the state of conductivity in the first current control member and to obtain a discharge through the luminescent tube of the energy stored in the first reactance means upon the state of nonconductivity in the first current control member.

4. The combination set forth in claim 3 wherein the first reactance means in inductive and includes a first winding connected in the electrical circuitry with the first and sec-0nd reactance means and the source of voltage connected in the electrical circuitry with the first and second reactance means and the source of voltage and includes a second winding connected to the luminescent tube and includes a third winding connected in an electrical circuit with the first winding and the current control member and the source of direct voltage to inhibit voltage surges during the change in the operation of the current control member between the conductive and nonconductive states.

5. In combination for illuminating a luminescent tube,

a source of direct voltage,

a current control member having an input electrode,

a control electrode and an output electrode,

a transformer having a primary and a secondary, the primary having first and second end terminals and an intermediate tap,

a capacitance,

a diode connected between the input and control electrodes of the current control member and connected in a series circuit with the capacitance and the primary of the transformer between the first end terminal and the intermediate tap of the primary,

a resistance connected between the control electrode and the output electrode of the current control member, means connecting the source of direct voltage vbetween the output terminal of the current control member and the second end terminal of the primary of the transformer, and

means connecting the luminescent tube to the secondary of the transformer.

6. The combination set forth in claim 5 wherein the transformer has a third winding and wherein the luminescent tube has a filament and wherein the filament is connected across the third winding of the transformer and wherein the third Winding of the transformer isconnected between the output terminal of the current control member and the source of direct voltage.

7. In combination for illuminating a luminescent tube,

a source of direct voltage,

a first current control member having conductive and nonconductive states,

first reactance means constructed to store energy and connected to the first current control member and to the source of direct voltage to receive a storage of energy when the first current control member is in the conductive state,

second reactance means constructed to store energy and connected to the first reactance means and to the first current control member to store energy when the first current control member is in the conductive state,

a second current control member connected to the first current control member and connected in electrical circuitry with the first and second reactance means to provide for a discharge of the second reactance means through the second current control member upon the storage of energy in the second reactance means to a particular value and to produce the state of nonconductivity in the first current control member during the discharge of the second reactance means through the second current control member and to inhibit any transient conditions in the first reactance means upon a change of the first current control member from the conductive state to the nonconductive state,

means connected to the first current control member to bias the first current control member to the state of conductivity for obtaining the first state of conductivity in the first current control member upon the discharge of the second reactance means to a second particular value different from the first particular value, and

means connecting the first reactance means to the luminescent tube to obtain a flow of current through the first reactance means and the luminescent tube during the state of conductivity in the first reactance means and to obtain a discharge through the luminescent tube of the energy stored in the first reactance means during the state of nonconductivity in the first current control member.

8. The combination set forth in claim 7 wherein the luminescent tube has a filament and wherein the first reactance means has a portion connected across the filament.

9. The combination set forth in claim 8 wherein the first reactance means is inductive and the second reactance means is capacitive.

10. In combination for illuminating a luminescent tube having a filament,

a source of direct voltage,

a transformer having first, second and third windings,

the third winding of the transformer being connected across the filament of the luminescent tube to provide a high impedance across the filament in the absence of a current through the third winding and to provide a reduced impedance across the filament in accordance with the flow of current through the third winding,

the second winding of the transformer being connected across the tube to produce a luminescence of the tube upon the heating of the filament in the tube by the second winding,

a current control member having conductive and nonconductive states and connected in a circuit with the first and third windings of the transformer and with the source of direct voltage to produce a flow of current through the first and third windings of the transformer during the state of conductivity in the first current control member,

means for biasing the current control member of the state of conductivity, and

capacitive means connected in a circuit with the current control member and the first winding of the transformer to become charged during the state of conductivity in the current control member and to become discharged upon becoming charged to a particular value and to bias the current control member to a state of nonconductivity during the discharge of the capacitance means.

11. The combination set forth in claim 10 wherein the first winding of the transformer is provided with an intermediate tap and wherein the current control member and the capacitance means are connected in the circuit with the first winding of the transformer at the intermediate tap in the primary winding of the transformer.

12. In combination for illuminating a luminescent tube,

a source of direct voltage,

a transformer having a primary winding and a secondary winding, the primary winding having first and second terminals and first and second intermediate taps at a pair of spaced positions along the winding,

a current control member having states of conductivity and nonconductivity and connected in a circuit with the source of direct voltage and the primary winding of the transformer between the first and second taps of the primary winding,

means biasing the current control member to the state of conductivity to obtain the flow of current through the circuit including the current control member, the source of direct voltage and the primary winding of the transformer,

charge storage means connected in a circuit with the current control member and the primary winding of the transformer between the first tap and the first end terminal of the primary winding to become charged during the state of conductivity in the current control member and to become discharged upon becoming charged to a particular value and to bias the current control member to the state of nonconductivity during such discharge,

the second end terminal of the primary winding of the transformer being connected to the current control member, and

means connecting the luminescent tube to the secondary winding of the transformer.

13. The combination set forth in claim 12 wherein the charge storage means include a capacitor and a second current control member to obtain a discharge of the capacitor through the second current control member and wherein the second current control member is connected to the first current control member to bias the first current control member to the state of nonconductivity during the time that the capacitor is discharging through the second current control member.

14. In combination for illuminating a luminescent tube, a source of direct voltage, a first current control member having conductive and nonconductive states, a second current control member having conductive and nonconductive states, an inductive reactance having first and second end terminals and an intermediate tap, a capacitance, means connecting the source of direct voltage, the first and second end terminals of the inductance reactance and the capacitance in electrical circuitry to bias the first current control member to a conductive state for obtaining a charging of the capacitance and a storage of energy in the inductive reactance during the operation of the first current control member in the conductive state, means connecting the capacitance, the second current control member and one of the end terminals and the intermediate tap of the inductive reactance in electrical circuitry for producing a discharge of the capacitance through the second current control member and the inductive reactance upon the charging of the capacitance to a particular value to obtain the 13 14 operation of the first current control member in the References Cited nonconductive state during the discharge of the ca- UNITED STATES PATENTS pacitance through the second current control mem- 2 982 881 5/1961 Reich 315 209 X and 3,016,478 1/1962 Kadell -i 315206 means connecting the luminescent tube to the lndllC- 5 3 i i tive reactance for energizing the inductive reactance. 15. The combination set forth in claim 14 wherein JOHN W. HUCKERT, Primary Examiner means are included for inhibltlng transient surges of volt- R. R POLISSACK, Assistant Examiner age durlng the change 1n the operatlon of the first current control member between the conductive and noncon- 10 ductive states. 315-219, 223, 238, 239, 240, 244, 245; 331-111, 112 

